Range of the operating functions is expanding and diversifying among various electronic apparatus developed recently. A cursor moving in a display or selection keys provided on a key board are increasingly used as means for selecting an operational function when using an apparatus. As a device for inputting signals in such apparatus, a switch having multiple functions is requested, in which switch one operating body can manage action of pluralities of switch elements. For satisfying the above needs, various types of multidirectional switches that can be operated in a number of directions have been proposed.
A conventional multidirectional switch is described in the following with reference to FIG. 12 through FIG. 15. FIG. 12 shows a cross sectional view of a conventional multidirectional switch, FIG. 13 is an exploded perspective view of the switch, FIG. 14 is a cross sectional view of the switch in a state when the operating body is being pressed at the center, FIG. 15 is a cross sectional view of the switch in a state when the operating body is being pressed at a peripheral place.
As shown in FIG. 12 and FIG. 13, the conventional switch comprises a switch substrate 1 provided on the upper surface with a pair of fixed contact points 1A for the center switch element and four pairs of fixed contact points 1B for the periphery switch elements disposed in the peripheral region; a driving body 2 placed on the switch substrate 1, which driving body 2 being formed of a base portion 2A of an almost-flat board shape, a center drive portion 2D having on the bottom surface a movable contact point 2B opposing to the fixed contact points 1A and connected at the bottom circumference with the base portion 2A by a dome-shaped connection portion 2C of thin wall thickness, and four periphery drive portions 2G disposed around the center drive portion 2D, each having on the bottom surface a movable contact point 2E opposing to the fixed contact points 1B, connected at the bottom circumference with the base portion 2A by a dome-shaped connection portion 2F of thin wall thickness.
An operating body 3 of a thick disc shape is making contact at the bottom center with the upper surface of the center drive portion 2D, and is provided with an engagement portion 3A for positioning surrounding side wall of the center drive portion 2D and a flange 3B protruding from the outer circumference, which flange 3B having a plurality of cuts 3C. A resin case 4 is having an opening 4B for allowing the operating body 3 to rise and a plurality of pillars 4A disposed on the reverse surface for engagement with a certain clearance to the cuts 3C.
In the normal state, clearance between the movable contact point 2B and the fixed contact points 1A is set to be smaller than the sum of a clearance B between the movable contact point 2E and the fixed contact points 1B plus a clearance C between the bottom surface of flange 3B of operating body 3 and the upper surface of periphery drive portion 2G. Namely, clearance A&lt;(clearance B+clearance C).
FIG. 12 illustrates the above described structure in the neutral state. When the operating body 3 is pressed down at the center as indicated with an arrow mark in FIG. 14, the center drive portion 2D moves down with flexion of the connection portion 2C, and the movable contact point 2B contacts with the fixed contact points 1A. Thereby, the center switch element turns into ON state. At this state, since the sum of clearances B and C is greater than the clearance A, the movable contact point 2E does not contact with the fixed contact points 1B; the periphery switch elements remain in OFF state. As soon as the pressure applied on the operating body 3 is withdrawn, the operating body 3 is pushed up by the center drive portion 2D with an elastic restorative force of the connection portion 2C. Thus it restores the neutral state.
When the operating body 3 is pressed at a peripheral region as illustrated with an arrow mark in FIG. 15, the operating body 3 tilts guided by the cut 3C of flange 3B and the pillar 4A. The connection portion 2C flexes and the bottom circumferential surface of operating body 3 makes contact with the upper surface of periphery drive portion 2G. With a further press, the connection portion 2F flexes allowing the periphery drive portion 2G to go down, and the movable contact point 2E contacts with the fixed contact points 1B. Thus ON state is created with the periphery switch elements. At this time, since the movable contact point 2B is set to maintain a certain clearance against the fixed contact points 1A, the fixed contact points 1A are not connected. Thus the center switch element is kept in OFF state. As soon as the pressure applied on the operating body 3 is withdrawn, the operating body 3 is pushed up by the center drive portion 2D and the periphery drive portion 2G with the elastic restorative force of connection portions 2C and 2F, and moves upward guided by the pillar 4A of resin case 4. Thus it restores to the neutral state.
In the conventional switch, however, there has been a problem that in some cases both the center switch element and the periphery switch element are brought into ON state altogether at a same time, if an operating force intended to press the operating body 3 at the center dislocated somewhat towards peripheral area, or if pressed with too much force although pressed at a right place.